Automatic load transfer switch



W. KOWALSKI AUTOMATIC LOAD TRANSFER SWITCH I July 9, 1968 2 Sheets-Sheet 1 Filed June 1, i966 b 70 9 23 Z r flttorngy' July 9, 1968 w. KOWALSKI AUTOMATIC LOAD TRANSFER SWITCH 2 Sheets-Sheet 2 Filed June 1. 1966 mmvrox. wits?" fizz/dish BY United States Patent Oflice 3,392,355 Patented July 9, 1968 3,392,355 AUTOMATIC LOAD TRANSFER SWITCH Walter Kowalski, Oak Creek, Wis., assignor to McGraw- Edison Company, Milwaukee, Wis., a corporation of Delaware Filed June 1, 1966, Ser. No. 554,418 13 Claims. (Cl. 335-60) ABSTRACT OF THE DISCLOSURE A transfer switch for monitoring the condition of a preferred energy source and automatically switching to an alternate energy source upon loss of energy of the preferred source. A relay coupled to a latch arrangement operates in response to de-energization of the preferred source to release the latch. A spring snaps the latch open when it is released and a lever arm attached to the latch strikes a second lever arm which rotates a switch to open the connection to the preferred source and close a connection to the alternate source. Manual means are provided to return the switch to the preferred source, close the latch and recharge the spring.

This invention relates to a transfer switch and more particularly to a switch for transferring a load system between preferred and alternate sources of supply.

Automatic switches for transferring a load circuit between a preferred and an alternate power source are well known. However, the application of these switches has been relatively limited because they are complicated and expensive.

It is an object of the invention to provide a new and improved switch mechanism for transferring a load circuit between a preferred and an alternate power source.

Another object of the invention is to provide a load transfer switch which is simple and economical.

Another object of the invention is to provide a transfer switch for automatically switching a load circuit from a preferred to an alternate power source and for manually returning the load circuit to the preferred source. A still further object of the invention is to provide such switches which may be operated to an off position from either the preferred or alternate positions.

These and other objects and advantages of the instant invention will become more apparent from the detailed description thereof taken with the accompanying drawings wherein:

FIG. 1 schematically illustrates the application of the load transfer switch according to the instant invention;

FIG. 2 is a perspective view of the load transfer switch incorporating the instant invention; and

FIGS. 3 and 4 illustrate the operating mechanism of the load transfer switch according to the invention in its preferred and alternate positions, respectively.

In general terms, the invention comprises a switching assembly the combination of a switch means movable between preferred and alternate positions, operating means operatively associated with the switch means for moving the same to its alternate position, stored energy means coupled to the operating means, holding means for holding the operating means in an energy stored position, condition sensing means operative upon the occurrence of a predetermnied condition to release the operating means for movement into an energy discharged position to move the switch means from the preferred to its alternate position, means for moving the switch means to its positions independently of said operating means, and reset means for returning the operating means to its energy stored position and for recharging the energy storage means,

Referring more specifically to FIG. 1, the transfer switch 9 according to the instant invention is shown to include a switch assembly 10 for connecting a load circuit symbolized by a transformer 11 between a preferred source P and an alterante source A. More specifically, the switch assembly 10 is provided with a movable blade 12 which normally engages a preferred contact 14 connected to the preferred source P. An operating mechanism 15 is operative upon the loss of power in the preferred source P to switch the blade 12 from the first fixed contact 14 to a position 12a wherein it engaged the second fixed contact 16 connected to the alternate source A. As will be described in more detail hereinafter, means are also provided for manually switching the blade 12 from engagement with the contact 16 to engagement with the contact 14 and also for moving the blade 12 to an off position 12b relative to the preferred source P and an off position 12c relative to the alternate source A.

The switch assembly 10 is shown more specifically in FIG. 2 to include a drive assembly 21 which is coupled between the operating mechanism 15 and the switch blades 12. The drive asembly moves the switch blades 12 from the preferred source contact 14 to the alternate source contact 16 when actuated by the operating mechanism 15. In addition the drive mechanism is operable to move the switch blade 12 to its alternate position 12a or to either of the off position 12b or 12c when actuated by manual operating eye 22.

A switch mounting plate 24 is shown in FIG. 2 to support the switch 10 and is in turn connected to the casing 25 which forms an enclosure for the operating mechanism 15. The switch drive asesmbly 21 is mounted between a first plate 26 secured to the mounting plate 24 and a second plate 27 which is secured to plate 26 by four posts 28.

The stationary contacts 14 and 16 are mounted on a contact plate 29 which is of suitable insulating material which is suspended from the plate 27 by tubular insulating spacers 30. The switch blade 12 is secured to and driven by a driven shaft 32 of insulating material and extending through a clearance aperture in the plate 27. The switch blade 12 also includes a rotary current interchange 33 for transferring current to a stationary terminal 34 which is electrically connected to the transformer 11 (see FIG. 1).

The details of the switch drive assembly 10 form no part of the instant invention and accordingly will not be discussed in detail for the sake of brevity. For purposes of understanding the instant invention, it is sufiicient to state that the manual operating eye 22 is mounted on a drive shaft 36 which is coupled to the driven shaft 32 by a ratchet and cam assembly, which are not shown, but which are surrounded by torsion springs 37. When the eye 22 is rotated approximately in either direction, the drive shaft 36 loads the torsion springs 37 but the ratchet assembly (not shown) will prevent the driven shaft 32 from rotating. After approximately an addition 45 of rotation, the cam assembly (not shown) will release the ratchet assembly (not shown) so that the driven shaft 32 and the switch blade 12 are snapped 90 to an alternate one of its positions. Additional manual operation in either direction of the switch blade 12 may be accomplished in the manner just described. For a more complete description of the switching assembly 10' just described, reference is made to co-pending application Ser. No. 482,730 filed Aug. 26, 1965, now Patent No. 3,316,367 and assigned to the assignee of the instant invention.

FIGS. 3 and 4 show the operating mechanism 15 to include a relay 40 for sensing the disappearance of power in the preferred source P, a gear assembly 41 for coupling the operating assembly 15 to the drive shaft 36, a stored energy assembly 42, a latch assembly 43 for holding the stored energy assembly 42 in a charged condition, and a time delay assembly 44 for preventing transient outages in the preferred source P from causing operation of the mechanism 15.

The gear assembly 41 includes a drive gear 46 afiixed to the drive shaft 36 and an operating gear 47 afiixed to a shaft 49 which rotates about a fixed axis. An operating arm 50 is also affixed to the shaft 49 and carries a laterally extending operating pin 52 at its free end,

The stored energy assembly includes a pair of toggle links 54 and 55 which are pivotally coupled by a knee pin 56. The other end of the link 54 is pivotally connected to a fixed pin 58 while the other end of the second toggle link 55 is pivotally connected by a pin 60 to the latch assembly 43. A stored energy spring 61 extends between the pins 58 and 60 and attempts to collapse the toggle links 54 and 55 from their extended position shown in FIG. 3 to their collapsed position shown in FIG. 4, but this is normally prevented by the latch assembly 43.

The latch assembly 43 includes a generally triangular latch plate 62 which is pivotally mounted at its apex about a fixed shaft 63 and which carries the pin 60 at one side of its base. A tumble member 65 is mounted for rotation about pin 60 and is urged in a counter-clockwise direction by spring 67 and against a stop pin 68 carried by the latch plate 62. In addition a latch member 70 is affixed to plate 62 at the other side of its base.

When the operating mechanism 15 is in its latched condition shown in FIG. 3, the latch member 70 engages a latch shaft 72 which is rotatable about a fixed axis and which has a half-cut-out portion 73. A latch lever 75 is fixed to the shaft 72 and a relay lever 76 is pivotally mounted about shaft 72 and the two are normally held in parallelism by a spring 77. A stem 78 extends from the relay 40 and is coupled by a pin 80 to the free end of the relay lever 76. In addition a drive pin 74 extends laterally from the relay lever 76 and through an enlarged opening 79 in the latch lever 75.

The time delay assembly 44 may be of any well known type, such as the hydraulic device illustrated in the drawings, wherein an operating arm 81 is pivotally mounted at 82 and engages a stem 83 of a hydraulic mechanism disposed within the casing 84. The hydraulic mechanism coupled to the stem 83 retards clockwise pivotal movement of the arm 81 as the latter is urged by a spring 85. The relay 40 is coupled to the arm 81 by a link 86 and when the former is energized, it holds the arm 81 in the unpivoted position shown in FIG. 3.

Referring again to FIG. 1 the relay 40 is shown to be connected across the secondary winding of transformer 11 by conductors 88 and 89 and normally closed contacts 90. As a result, the relay 40 is energized and maintains the operating mechanism 15 in its latched position shown in FIG. 3. Should the transformer 11 be disconnected from the preferred source P, such as by the opening of circuit breaker 92, the relay 40 will be de-energized. Upon the latter event, the spring 85 is no longer restrained and begins to pivot the arm 81 from its position shown in FIG. 3 to its position shown in FIG. 4. This pivots the relay member 76 clockwise so that the latch lever 75 and the latch shaft 72 also rotate clockwise. When latch shaft 72 has pivoted to the point where its cut-out portion 73 has passed the latch member 70, the latch assembly 43 will be released for pivotal movement from its position shown in FIG. 3 to its position shown in FIG. 4 under the influence of the stored energy spring 61. The engagement between the drive pin 74 and the periphery of opening 79 in latch lever 75 insures that the latter will rotate with lever 76 despite the frictional force between the latch member 70 and latch shaft 72.

As the latch assembly 43 pivots, the tumble member 65 will impact the pin 52 extending from the operating arm 50 afiixed to the shaft 49. This rotates the arm 50, the shaft 49 and the operating gear 47 through approximately 67 /2 in the counter-clockwise direction so that the drive gear 46 is rotated approximately 135 clockwise. As a result the switch blade 12 is snapped from its preferred position wherein it engages contact 14 to its alternate position wherein it engages contact 16. The torsion springs 37 then return the drive gear approximately 45 counterclockwise and the operating gear 47 approximately 22 /2" clockwise to their positions shown in FIG. 4.

Referring again to FIG. 1 it can be seen that movement of the switch blade 12 from the preferred contact 14 to the alternate contact 16 will again energize the transformer 11, assuming of course that circuit breaker 93 is closed and energy is available in the alternate source A. The relay 40 however remains de-energized because the contact 90, which is coupled to the operating mechanism 15, is moved to its opened position when the operating mechanism moves to its position shown in FIG. 4.

After service has been restored to the preferred source P, the gear 46 may be rotated approximately 135 counter-clockwise as viewed in FIG. 4, by rotating the eye 22. This moves the switch blade 12 from the alternate contact 16 to the preferred contact 14 wherein the torsion springs 37 return the gear 46 and the eye 22 approximately 45 to their phantom positions shown in FIG. 4. This movement of the gear 46 also rotates the operating gear 47 from its position shown by full lines in FIG. 4 to its position shown by phantom lines. I addition, such return movement of the gears 46 and 47 recloses contact to re-energize the relay 40 whereupon the relay lever 76, the latch lever 75 and the latch shaft 72 are rotated from their positions shown by full lines to their positions shown by phantom lines in FIG. 4.

The latch assembly 43 may then be relatched in its position shown in FIG. 3. This is accomplished by pulling on a hook-operated lever 94 (see FIG. 1) which is coupled to one end of a cable 95 which is wound around a fixed pulley 96 and which is connected to the knee pin 56 of the stored energy assembly 42. When the cable 95 is pulled downwardly as viewed in FIG. 4, the toggle links 54 and 55 move from their collapsed position shown in FIG. 4 to their approximate straight line position shown in FIG, 3. This forces the latch plate 62 counter-clockwise to its latched position shown in FIG. 3. As the latch plate 62 moves from its position shown in FIG. 4 to its position shown in FIG. 3, the tumble member 65 will engage the pin 52 on the operating arm 50 and will rotate through a slight clockwise angle around pin 60 and against spring 67 until it has cleared pin 52 whereupon spring 67 will return it to its unpivoted position shown in FIG. 3. In addition, as the latch member 70 moves into its position shown in FIG. 3, it will strike the flat surface of the cut-out portion 73 on latch shaft 72 to rotate said shaft through a slight clockwise angle. While the relay 40 prevents rotation of the relay lever 76, the latch lever 75 is free to rotate and against the influence of spring 77 because of the opening 79 in the latch lever 75 which moves away from the drive pin 74. After the latch member 70 has moved passed the cut-out portion 73, the spring 77 returns the latch lever 75 into an aligned position relative to the relay lever 76.

A first signal light 100 is shown in FIG. 1 to be connected across the conductors 88 and 89 and through contacts 101 which are coupled to the operating mechanism 15 and which are opened when the operating mechanism is in its latched condition and which are closed when the operating mechanism is released. Thus the signal light 100 will indicate whenever the operating mechanism 15 is unlatched. In addition a test lamp 102 is connected and parallel with the relay 40 through a push button 103 so that it can be determined whether or not the relay 40 is energized.

It can be seen from FIGS. 3 and 4 that the switch 10 may be manually stepped to any of its positions without interference from the operating mechanism 15. Thus the switch blade 12 may be stepped from its preferred position to its preferred off position 12b by rotating the eye 22 and the gear 46 counterclockwise as viewed in FIG. 3 or from its preferred position to its alternate position 12a by rotating the eye 22 and the gear 46 clockwise. Such motion will be unimpeded by the tumble member 65 because regardless of whether the mechanism 15 is in its latched position shown in FIG. 3 or its unlatched position shown in FIG. 4, the tumble member will not lie in the the path of the pin 52 so that the operating arm 50 is free to rotate in either direction.

While only a single embodiment of the invention has been shown and described other modifications thereof will become apparent to those skilled in the art once the invention is known. Accordingly it is not intended to limit the invention to the single disclosed and illustrated embodiment but only by the scope of the appended claims.

I claim:

1. In a switching assembly connected in an electrical circuit, the combination of switch means having preferred and alternate contacts and including movable contact means selectively engageable with said preferred and alternate contacts, movable lever means attached to the movable contact means and having an energy charged position and an energy discharged position and including first and second movable members spaced apart when the lever means is in either of its two positions and engaging each other when the lever means is intermediate said positions for moving the movable contact means between the preferred and alternate contacts, the positions at which the movable contact means engages the preferred and alternate contacts respectively corresponding to the energy charged and energy discharged positions of the movable lever means, condition sensing means connected in said electrical circuit for sensing the energy condition of the electrical circuit and operatively moving in response to the occurrence of a predetermined energy condition in the electrical circuit, releasable holding means for holding said movable lever means in its energy charged position wherein the movable contact means engages the preferred contact and including release means attached to said condition sensing means and being responsive to operation of the condition sensing means when said pre determined energy condition occurs to release the lever means and stored energy means coupled to said movable lever means for moving the lever means from its energy charged position to its energy discharged position wherein the movable contact means engages the alternate contact and being actuated when the releasable holding means is released by operation of the condition sensing means upon occurrence of said predetermined energy condition in the electrical circuit.

2. The switching assembly set forth in claim 1 wherein said switch means comprises a snap acting, multiposition switch.

3. The switching assembly set forth in claim 1 and including time delay means coupled to said condition sensing means for delaying the operation thereof.

4. The switch assembly set forth in claim 1 wherein said switch means includes a manual drive means attached to said movable contact means for moving said movable contact means independently of said movable lever means and between said preferred and alternate contacts and off positions relative thereto.

5. The switching assembly set forth in claim 1 and including drive means secured to said movable contact means for moving said movable contact means independently of said movable lever means and reset means attached to said energy storage means for returning said movable lever means to its energy charged position and for recharging said energy storage means.

6. The switching assembly set forth in claim 5 wherein said storage energy means comprises a spring means attached to said releasable holding means and a collapsible linkage, said reset means is attached to the collapsible linkage and is manually operable to charge said spring means and to extend said linkage and said releasable holding means includes latch arm means engagingly restrained by the release means when the movable lever means is in its energy stored position for holding said spring means in a charged condition and said linkage in an extended condition.

7. The switching assembly set forth in claim 5 wherein said drive means includes gear means connected to said movable lever means and to said movable contact means and being movable through a predetermined angle to move said movable contact means between each of said preferred and alternate contact positions and said off positions, said movable lever means moving said gear means and said movable contact means when the movable lever means moves between its said two positions.

8. The switching assembly set forth in claim 7 wherein said manual. drive means includes shaft means, said gear means includes first and second gears, one of said ears being afiixed to said shaft means and the other being relatively larger, movement of said gear means through a predetermined angle being operative to move said movable contact means between each of said preferred and alternate contant positions and said oif positions and said movable lever means moves said gear means and said movable contact means when the movable lever means moves between its said two positions.

9. The switch assembly set forth in claim -1 wherein said stored energy means comprises a spring means attached to said holding means and a collapsible linkage.

10. The switching assembly set forth in claim 9 wherein said releasable holding means includes latch arm means having a reset position in which it is engagingly restrained by the release means when the movable lever means is in its energy stored position and in which it holds said sprin means in a charged condition and said linkage in a rigid condition.

11. The switching assembly set forth in claim 10 and including time delay means coupled to said condition sensing means for delaying the operation thereof.

12. The switching assembly set forth in claim 10 wherein said condition sensing means includes a relay means having an arm secured to the releasable holding means and the time delay means and being electrically connected to said electrical circuit for sensing the energy condition of the electrical circuit.

13. The switching assembly set forth in claim 10 wherein said release means includes'a pivotally mounted latch member attached to said relay means and being pivotable into a reset position when said relay means is energized in which it engagingly restrains said latch arm means when the latch arm means is in its reset position and being pivotable into a released position when said relay means is de-energized in which it releases the latch arm means, drive means connected to said movable contact means for moving said movable contact means independently of said movable lever means and contact means coupled to and operated by said drive means and electrically connected between the electrical circuit and the relay means for completing the electrical connection between the relay means and the electrical circuit when said movable contact means is in its preferred contact position and for opening the electrical connection between the relay means and the electrical circuit when said movable contact means is out of its preferred contact position.

References Cited UNITED STATES PATENTS 2,810,804 10/1957 A. Van Ryan 335-27 3,132,255 5/1964 Spinelli et a1. 30764 BERNARD A. GILHEANY, Primary Examiner. H. BROOME, Assistant Examiner. 

